Electromagnet having yieldable pole piece members



Sept. 14, 1965 H. A. ENGE 3,206,654

ELECTROMAGNET HAVING YIELDABLE POLE PIECE MEMBERS Filed June 24, 1963 United States Patent 3,206,654 ELECTROMAGNET HAVING YIELDABLE POLE PIECE MEMBERS Harald A. Enge, Winchester, Mass, assignor to High Voltage Engineering Corporation, Burlington, Mass., a corporation of Massachusetts Filed June 24, 1963, Ser. No. 289,891 2 Claims. (Cl. 317-158) This invention relates to magnets, and in particular, to magnets having a gap between a pair of pole faces. Briefly stated, my invention comprehends apparatus for preventing the attractive force between the pole faces from bending them or the yoke or otherwise distort the iron-structure so as to upset the field distribution in the gap. The invention is particularly useful in magnetic spectroscopy. However, the invention is not limited to this application and although in the following detailed description, particular reference will be made to magnetic spectroscopy, it is to be understood that the invention is not limited to such an application but includes any magnet wherein it is desired to prevent distortion of the pole faces caused by the attractive force across the gap between the pole faces.

The invention may best be understood from the following detailed description thereof having reference to the accompanying drawing in which:

FIG. 1 is a plan view of a magnet embodying the invention and FIG. 2 is a cross sectional view of the same, along the line 22 of FIG. 1 but to a somewhat enlarged scale.

Referring to the drawing, therein is shown a magnet 1 which is energized by suitable coils 2. A gap 3 is maintained between two pole pieces 4, 5 which are separated by spacers 6, 7 of brass or other non-magnetic alloy. A return path is provided by a yoke 8 which may be one piece or made up of several pieces of magnetic material. In the conventional magnet, the only gap in the magnetic circuit is the principal gap between the two pole pieces. In such an arrangement non-magnetic spacers may maintain the separation between the pole pieces at the periphery of the gap, or the yoke may be stitf enough to maintain a reasonably constant spacing. However, the magnetic force of attraction between the pole faces tends to pull them together with some distortion as a result. In accordance with the invention, I introduce two auxiliary gaps 9, 10 between each of the pole pieces 4, 5 and the yoke 8 and I provide spacers 11, 12 of brass or other nonmagnetic alloy in one of the auxiliary gaps (the lowermost in FIG. 1, as shown at 10). These spacers 11, 12 are located in positions similar to those occupied by the spacers 6, 7 in the main gap 3. In accordance with the invention, no such support is provided in the other auxiliary gap 9, but instead spring loaded members 13, 14 or similar devices are provided to exert a force against the adjacent pole piece 4 sufiicient to support the weight of that pole piece in the event that the magnet should be tilted or turned upside down, and to support a possible 3,206,654 Patented Sept. 14, 1965 unbalance between the magnetic forces exerted on the two sides of a pole piece. The gravitational forces on the pole pieces are normally quite insignificant compared with the magnetic forces involved.

It will be observed that in the case of magnets where the linear dimensions of the pole areas are large compared to the thickness of the pole pieces, the magnetic flux in the auxiliary gaps is practically identical to the flux in the main gap. The resulting forces on both sides of a pole piece will then practically balance each other and no appreciable distortion will be experienced. The mechanical member which now has to sustain an unbalanced force is the yoke, and by means of the spring loaded contacts the deflection of the yoke is taken up by the springs and only an insignificant change in the spring forces is transmitted to the pole pieces. Of course, the spring loaded members 13, 14 can be replaced by any yielding member which will permit deflection of the yoke 8 without transmitting this deflection to the pole pieces 4, 5.

The lower auxiliary gap 10 is not essential to the invention, but is preferably utilized in order to prevent bending of the adjacent pole pieces 5 if the yoke 8 bends and also to balance the reluctance introduced by the upper auxiliary gap 9.

Having thus described the principles of the invention together with an illustrative embodiment thereof, it is to be understood that although specific terms are employed, they are used in a generic and descriptive sense and not for purposes of limitation, the scope of the invention being set forth in the following claims.

I claim:

1. A magnet having a pair of pole pieces separated by a gap and a yoke providing at least one return path for the magnetic field, said yoke being separated from one of the pole pieces by an auxiliary gap so that mechanical movement of deflection of said yoke is not transmitted to said pole piece, said magnet including rigid non-magnetic spacer means separating the pole pieces from one another and yieldable supporting means in said auxiliary gap separating said pole piece from said yoke.

2. A magnet having a pair of pole pieces separated by a gap and a yoke providing at least one return path for the magnetic field, said yoke being separated from each of the pole pieces by an auxiliary gap, said magnet including rigid non-magnetic spaced means separating the pole pieces from one another and yieldable supporting means in at least one of said auxiliary gaps separating the pole piece adjacent to said auxiliary gap from said yoke so that mechanical movement of deflection of said yoke is not transmitted to said pole piece.

References Cited by the Examiner UNITED STATES PATENTS 2,917,682 12/59 Kirchner et a1. 317-158 2,962,636 11/60 Purcell 317-458 JOHN F. BURNS, Primary Examiner. 

1. A MAGNET HAVING A PAIR OF POLE PIECES SEPARATED BY A GAP AND A YOKE PROVIDING AT LEAST ONE RETURN PATH FOR THE MAGNETIC FIELD, SAID YOKE BEING SEPARATED FROM ONE OF THE POLE PIECES BY AN AUXILIARY GAP SO THAT MECHANICAL MOVEMENT OF DEFLECTION OF SAID YOKE IS NOT TRANSMITTED TO SAID POLE PIECE, SAID MAGNET INCLUDING RIGID NON-MAGNETIC SPACER MEANS SEPARATING THE POLE PIECES FROM ONE ANOTHER AND YIELDABLE SUPPORTING MEANS IN SAID AUXILIARY GAP SEPARATING SAID POLE PIECE FROM SAID YOKE. 